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Thursday, 23 April 2015

Scientists genetically modify a human embryo for the first time: Controversial technique could lead to designer babies

Chinese scientists have admitted to changing the genes of human embryos for the first time.

The announcement confirms rumors that some researchers have been conducting ethically questionable genetic experiments.

Some scientists have already reacted with horror at the idea, for fear it could be misused to allow parents to 'select' the genes they will pass on to their grandchildren.

HOW WAS IT DONE?

The team tried to tweak the gene responsible for β-thalassaemia, a potentially deadly blood disorder, using a germ line editing technique known as CRISPR/Cas9.

CRISPR technology precisely changes target parts of genetic code.

Unlike other gene-silencing tools, the CRISPR system targets the genome's source material and permanently turns off genes at the DNA level.

The DNA cut – known as a double strand break – closely mimics the kinds of mutations that occur naturally, for instance after chronic sun exposure.

But unlike UV rays that can result in genetic alterations, the CRISPR system causes a mutation at a precise location in the genome.

When cellular machinery repairs the DNA break, it removes a small snip of DNA. In this way, researchers can precisely turn off specific genes in the genome.

The team studied the ability of the CRISPR/Cas9 system to edit the gene called HBB responsible for β-thalassaemia

However, others argue that the technology could also be used to rid families of devastating inherited diseases like cystic fibrosis or certain cancers.

Researchers at Sun Yat-sen University in Guangzho have today published their research in the journal Protein & Cell, according to a report in Nature.

In the paper, researchers led by Junjiu Huang, attempted to downplay concerns by using 'non-viable' embryos, which can't develop into babies.

The team tried to tweak the gene responsible for β-thalassaemia, a potentially deadly blood disorder, using a germ line editing technique known as CRISPR/Cas9.

But the researchers involved said that their results revealed 'serious obstacles' in using the technique on human embryos.

CRISPR technology precisely changes target parts of genetic code.

Unlike other gene-silencing tools, the CRISPR system targets the genome's source material and permanently turns off genes at the DNA level.

The DNA cut – known as a double strand break – closely mimics the kinds of mutations that occur naturally, for instance after chronic sun exposure.

But unlike UV rays that can result in genetic alterations, the CRISPR system causes a mutation at a precise location in the genome.

When cellular machinery repairs the DNA break, it removes a small snip of DNA. In this way, researchers can precisely turn off specific genes in the genome.

Huang's group studied the ability of the CRISPR/Cas9 system to edit the gene called HBB.

The team injected 86 embryos and then waited two days for the CRISPR technique to work.

Nature reports that of the 71 embryos that survived, 54 were genetically tested. The tests found that 28 were successfully spliced, but only a few contained the replacement genetic material.

'If you want to do it in normal embryos, you need to be close to 100 per cent,' Huang told Nature. 'That's why we stopped. We still think it's too immature.'

Until now scientists have concentrated on using genome editing techniques on somatic cells - non-reproductive cells like those found in skin, muscle, nerves, bone and liver for example - to help them study diseases.

Modifying the DNA of human embryos so that DNA changes are preserved in the germ line - the sperm and eggs - means such alterations can be passed on to future generations.

ARE DESIGNER BABIES ON THE HORIZON?

Improvements in genetics are causing designer babies to near '100 per cent efficiency' in trials using mice, a leading scientist has warned.

Dr Tony Perry, a geneticist at the University of Bath, said that society needed to be prepared for the day parents can choose certain traits in their children.

The warning follows a breakthrough last April in which scientists were able to cure a genetic liver disease in living, adult mice using the CRISPR-Cas9 gene editing technique.

The CRISPR technology precisely changes target parts of genetic code and could be used to create designer babies.

'We used a pair of molecular scissors and a molecular sat nav that tells the scissors where to cut,' Dr Perry told James Gallagher at the BBC. 'It's a case of 'you shoot you score'...On the human side, one has to be very cautious.'

Unlike other gene-silencing tools, the CRISPR system targets the genome's source material and permanently turns off genes at the DNA level.

Such work is already illegal in many countries around the world including the UK, but is permitted in the US and China.

A number of other groups around the world are thought to be working on techniques to genetically modify human embryos.

Xingxu Huang, from Shanghai Tech University in China has been seeking permission to perform the technique on discarded human embryos after having successfully using it to modify monkey embryos that developed into live animals.

Professor George Church, a geneticist at Harvard Medical School is also said to be developing techniques that could be used to modify human embryos.

Dr Luhan Yang, a scientist with Church's group, recently outlined proposals to edit the human germline in an interview with Technology Review.

She proposed using immature egg cells from the ovaries taken from women undergoing surgery for ovarian cancer.

The immature egg would be grown and coaxed into dividing before a gene-editing technique known as CRISPR would be used to correct the genetic fault that was causing the ovarian cancer.

However, the project is not thought to be underway yet and it is not known if it has been approved.

Dr Yang, however, has been reported to have been involved in a similar project in China.

Last month a leading group of biologists called for a worldwide moratorium on germ line research amid rumours that it had already been used to alter human embryos in China.

Edward Lanphier, chairman of the Alliance for Regenerative Medicine in Washington DC, and four colleagues, wrote in the journal Nature that such research could harm other areas of science by provoking a public outcry.

They wrote: 'It is thought that studies involving the use of genome-editing tools to modify the DNA of human embryos will be published shortly

'In our view, genome editing in human embryos using current technologies could have unpredictable effects on future generations.

'This makes it dangerous and ethically unacceptable.

'Such research could be exploited for non-therapeutic modifications.

'We are concerned that a public outcry about such an ethical breach could hinder a promising area of therapeutic development, namely making genetic changes that cannot be inherited.

'At this early stage, scientists should agree not to modify the DNA of human reproductive cells.'

Their fears tap into concerns that such technology could be used to create 'designer families' where certain traits are selected for.

In reality such selection can be difficult as often there is no single gene that provides a single trait and many genes have multiple functions.